GB/T 40401-2021 in English
VALIDDetermination of density by volumetric displacement—Skeleton density by gas pycnometry
- Issued on:2021-08-20
- Implemented on:2022-03-01
- File Format:PDF
- Delivery:Via email within 1~3 business days
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《GB/T 40401-2021骨架密度的测量 气体体积置换法》由TC168（全国颗粒表征与分检及筛网标准化技术委员会）归口，主管部门为国家标准化管理委员会。
Introduction
Analysis of the core content of the standard
Measurement principle and technical characteristics
This document specifies the standard method for determining the skeleton density of solid materials by means of a gas density meter. The technical core is based on the ideal gas state equation:
- Gas displacement principle: Volume displacement is performed under isothermal conditions using an inert gas (usually helium)
- Volume calculation: The volume of the sample solid skeleton is derived by measuring the pressure change before and after the expansion of the gas chamber and combining Boyle's law
- Density formula: ρs = msample/Vsolid
Instrument structure and measurement requirements
| Components | Technical requirements | Calibration requirements |
|---|---|---|
| Gas density meter | Dual gas chamber structure (sample chamber + reference chamber), pressure sensor accuracy ≤0.1%FS | Must be recalibrated after temperature changes |
| Analytical gas | Helium purity ≥99.996%, or nitrogen/argon (special samples) | Gas pipelines require regular leak detection |
| Reference samples | Stainless steel calibration balls, volume traceable to national benchmarks | Standard materials within the validity period of the certificate |
Key implementation points
Sample pretreatment specifications
- Drying treatment: Freeze drying is recommended for heat-sensitive materials, and conventional samples are dried at 105℃ for 2 hours
- Delamination requirements: Microporous materials need to be vacuum degassed to 10-3 Pa level
- Weighing control: Balance accuracy 0.1mg, weighing error <0.1%
Calibration procedure essentials
Determine the volume of the gas chamber by the secondary expansion method:
| Steps | Operation | Calculation formula |
|---|---|---|
| Calibration I | Expansion of empty sample chamber | Vcell=(pⅠ.2/pⅠ.1-pⅠ.2)·Vref |
| Calibration Ⅱ | Expansion with standard ball | Vcell=Vcal+(pⅡ.2/pⅡ.1-pⅡ.2)·Vref |
Technology Evolution and Industry Application
Compared with the traditional liquid displacement method, the technical advantages of the gas volume displacement method are:
- The measurement range is extended to 0.1-500cm3 samples
- Materials with an open porosity greater than 99% can be detected
- Stronger adaptability to irregularly shaped samples
Typical application areas: catalyst carrier density determination, battery material porosity analysis, pharmaceutical powder true density detection, etc.
Interference Factor Control Plan
| Interference Type | Influence Degree | Solution |
|---|---|---|
| Thermal Imbalance | ±0.5% Density Deviation | Extend the Balance Time to More Than 30min |
| Helium Permeation | The Error of Organic Materials Can Reach 3% | Switch to Nitrogen or Sulfur Hexafluoride |
| Insufficient Sample Amount | Volume Measurement Error Amplification | Ensure that the Sample Occupies 2/3 of the Volume of the Container |
Sample only — not a preview of GB/T 40401-2021
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